Wireless technologies have been used in the field of information application such as wireless transmission of signals for a long time, but the power transmission characteristic of such technologies has not been properly developed. An electronic device for daily use must be equipped with a dedicated power adapter to electrically connect to the Alternating Current (AC) utility power supply, or be equipped with a battery providing electrical energy to the electronic device. However, since the existing power adapter needs to use a power line to electrically connect to the electronic device, it is extremely inconvenient due to the limitation of the power line when the electronic device is moving. With the development of technology, the wireless power supplying technology has been developed to transmit electrical energy to the electronic device in a wireless manner. Reference is now made to FIG. 1, which depicts a schematic diagram of an existing wireless power supplying system. As shown in FIG. 1, the existing wireless power supplying system 100 includes an electric power transmitting unit 110 and an electric power receiving unit 120. The electric power transmitting unit 110 generally includes a power supply 111, a control circuit 112, an oscillating circuit 113 and a transmitting coil 114. The electric power receiving unit 120 generally includes a receiving coil 121 and a rectifying and filtering circuit 122. The power supply 111 of the electric power transmitting unit 110 is used for converting the AC utility power supply voltage to a Direct Current (DC) voltage required for each of the circuits in the electric power transmitting unit 110 (e.g., the control circuit 112 and the oscillating circuit 113), the oscillating circuit 113 is used to generate a frequency signal, the control circuit 112 is electrically connected to the oscillating circuit 113 to control a master frequency f0 of the frequency signal generated by the oscillating circuit 113, and the transmitting coil 114 generates a resonance frequency f1 based on the master frequency f0 of the frequency signal so as to output the electric power. The receiving coil 121 of the electric power receiving unit 120 is electromagnetically coupled to the transmitting coil 114 to receive the electric power outputted by the electric power transmitting unit 110, so as to generate an AC voltage having a certain resonance frequency f2, and the rectifying and filtering circuit 122 is used for converting that AC voltage to the DC voltage.
However, in order to enable the wireless power supplying system 100 to be operated stably, the master frequency f0 of the frequency signal generated by the control oscillating circuit 113, the resonance frequency f1 of the transmitting coil 114 and the resonance frequency f2 of the receiving coil 121 should be ideally equal (i.e. f0=f1=f2), so that the transmitting coil 114 and the receiving coil 121 can be electromagnetically coupled deeply, so as to generate the electrical energy at the electric power receiving unit 120 to implement wireless power supplying. However, in fact, due to the influences of physical characteristics, application environments and qualities of electrical elements and the like, there exists a shift between the resonance frequency f1 of the transmitting coil 114 and the resonance frequency f2 of the receiving coil 121, which causes a big difference and mismatch between the resonance frequency f1 of the transmitting coil 114 and the resonance frequency f2 of the receiving coil 121, and the deep electromagnetic coupling may not be enabled, and therefore the output power of the wireless power supplying system 100 is unstable, that is, the wireless power supplying system cannot operate normally.